1. Field
The invention is in the field of containment devices and systems for wash fluid, generally wash water, used in washing objects such as vehicles and equipment where the wash water after washing may have contaminants or a high solids content such as when washing dirt, oils, and mud from a vehicle.
2. State of the Art
With increased concern for the environment, washing items, particularly large items such as vehicles, can raise a problem of containment and disposal of wash fluid, usually water. The wash fluid can contain various contaminants ranging from soap, detergent, and wax which may be added to the fluid prior to washing; gasoline, oil, and grease that may be washed from a vehicle or other piece of equipment; to various other contaminants and solids that build up on a vehicle or other equipment during use and are washed off with the wash fluid.
Permanent wash sites have washing pads which collect the used wash fluid and direct it into a drain or collect it in a below grade open tank like structure or holding basin from which it can be pumped for disposal. Usually a grate is placed over the holding tank structure to form a surface on which the vehicle or other equipment to be washed may be located for washing. The wash fluid flows from the object being washed, through the grate, and into the holding tank. With open holding tanks, wastewater builds up with inevitable formation of bacteria which create health hazards and odor. Holding tanks for hazardous waste may also require construction of secondary containment systems and alarm systems in many locations. Also, such permanent sites now may require special permitting since they contain what may be considered as hazardous materials. A further problem is that during washing of an item it may be difficult for an operator to keep the fluid jet used for washing from impacting the fluid in the basin. When it does, dirty fluid, including oil floating in the fluid basin, is splashed on the object being cleaned and on the operator. This not only requires that the object to be cleaned again, but it also creates operator hazards because of the chemical and biological agents contained in the basin.
To clean a permanent holding tank, the access grate or manway must be removed and the waste extracted by draining, vacuuming, shoveling, or pumping. Such cleaning is difficult, time consuming, and renders the washing pad unusable during such cleaning.
A number of portable wash water containment devices have been proposed. Most of these take the form of an open top tank or pan over which a grate is placed to form a surface that supports the vehicle or other item to be washed. The wash water then flows from the item being washed, through the grate, and into the tank, see, for example, U.S. Pat. No. 6,021,792. A special waffle collecting and drainage pan may be used in the tank as in U.S. Pat. No. 5,738,139. In some cases, the equipment is merely placed in the tank with no supporting surface grate and the tank may merely be a waterproof membrane extending over an area bounded by raised sides, the membrane forming the water holding tank, see U.S. Pat. Nos. 5,547,312 and 5,597,001. The fluid may be drained from the tank in various ways such as through a drain or into a sump from which it can be pumped. As indicated, with vehicle washing, significant amounts of solids may be washed from the vehicle and settle in the tank. These solids build up and can easily plug any drain provided or fill up any sump provided. To remove such solids or other debris that may collect, it is necessary to remove any grate or other support surface provided to allow access to the tank. This is difficult and time consuming and renders the washing pad unusable during the cleaning process. If no surface above the holding tank is provided, the equipment sits in the holding tank with the collected wash fluid. The holding tank still has to be cleaned, and probably more often than when a surface above the tank is provided, so that the item to be washed does not sit in a puddle of mud and fluid.
Another problem with portable systems is that the collecting tanks are relatively shallow. With relatively shallow tanks, a slight variation in elevation, such as when placed on an uneven surface, can cause one end of the tank to be dry while another overflows, defeating the purpose of using the tank. If the deep end does not contain a suitable drain, it is virtually impossible to remove fluid from the tank. Further, the capacity of the tank is seriously reduced in such situations which then requires more frequent clearings.